Mental Chemistry is a book written by Charles F. Haanel, who is widely known at the author of the popular Master Key System book and as an important writer of the New Thought movement. In Mental Chemistry, Haanel states that mental chemistry is the science which treats the changes which material conditions undergo through the operations of the mind, verified by exact observation and correct thinking. This is an excellent book for individuals who are interested in reading a less common yet key work by Charles Haanel, and for those who enjoy reading books from the New Thought movement.